by Jeffrey D. Sachs - Tacloban in the Philippines has joined the growing list of cities – including New Orleans, Bangkok, Moscow, New York, Beijing, Rio de Janeiro, and Port-au-Prince, to name just a few – pummeled in recent years by climate catastrophes. So the global development agenda should empower cities to help lead the way to sustainability.
NEW YORK – Tacloban in the Philippines has now joined  the growing list of cities – including New Orleans, Bangkok, Moscow, New York,  Beijing, Rio de Janeiro, and Port-au-Prince, to name just a few – pummeled in  recent years by climate catastrophes. Many of the world’s largest cities, built  on seacoasts and rivers, face the threat of rising sea levels and intensifying  storms. So the new global development agenda now taking shape should empower  cities to help lead the way to sustainable development in the twenty-first  century. 
The importance of cities in today’s world economy is  unprecedented. Until the Industrial Revolution, human history was overwhelmingly  rural. Only around 10% of people lived in cities. Today, the share  of urbanites is around 53% and is likely to rise to around 67% by 2050. 
Because  per capita incomes are higher  in cities than in rural areas, the world’s cities today are estimated to account  for more than 80% of global income, with the largest 600 accounting for around  half. Most of the new jobs over the next few decades will be created in cities,  offering livelihoods to hundreds of millions of young people and, as China and  Brazil have demonstrated, helping to slash extreme poverty. 
Cities are also the innovation hubs for public policy.  Every day, mayors are called on to get the job done for residents. They are the  ones responsible for providing safe water, garbage collection, safe housing,  infrastructure, upgraded slums, protection from disasters, and emergency  services when catastrophes hit. So it is not surprising that while national  governments often are paralyzed by partisan politics, city governments foster  action and innovation. 
In the United States, for example, Martin O’Malley,  Baltimore’s former mayor and now Maryland’s popular governor, pioneered the use  of advanced information systems for urban management. New York City’s outgoing  mayor, Michael Bloomberg, worked relentlessly to implement a new sustainability  plan (called PlaNYC). And  the city’s incoming mayor, Bill de Blasio, is championing a bold program of  educational innovations to narrow the vast gaps in income, wealth, and  opportunity that divide the city. 
Sustainable development offers a new concept for the  world economy in the twenty-first century. Rather than focusing solely on  income, sustainable development encourages cities, countries, and the world to  focus simultaneously on three goals: economic prosperity, social inclusion, and  environmental sustainability. 
Economic prosperity speaks for itself. Social  inclusion means that all members of society – rich and poor, men and women,  majority and minority groups – should have equal rights and equal opportunities  to benefit from rising prosperity. And environmental sustainability means that  we must reorient our economies and technologies to provide basic services like  safe water and sanitation, combat human-induced climate change, and protect  biodiversity. Achieving these three goals will require good governance, public  finance, and effective institutions. 
Cities will be in the front lines of the battle for  sustainable development. Not only do they face direct threats; they also have  the best opportunities to identify and deliver solutions. As high-density,  high-productivity settlements, cities can provide greater access to services of  all kinds – including energy, water, health, education, finance, media,  transport, recycling, and research – than can most rural areas. The great  challenge for cities is to provide this access inclusively and sustainably. 
A significant part of the solution will come through  advanced technologies, including information systems and materials science. The  information and communications revolution has spawned the idea of the “smart  city,” which places the relevant technologies at the heart of systems that  collect and respond to information: smart power grids, smart transport networks  (potentially including self-driving vehicles), and smart buildings and zoning. 
The advances in materials science open the possibility  of much more energy-efficient residences and commercial buildings. Cities also  give rise to the opportunity to combine public utilities, as when urban power  plants use the steam released in electricity generation to provide hot water and  heating to residents. 
Yet technology will be only part of the story. Cities  need to upgrade their governance, to  allow for a greater role for poorer and more marginalized communities, and to  enable much more effective coordination across city lines when a metropolitan  area is home to many individual cities. Metropolitan governance is therefore  crucial, as smart cities require networks that operate at the metropolitan  scale. 
When the metropolitan scale is recognized, the  importance of leading urban areas is even more remarkable. New York City has  around 8.4 million people, but the NYC metropolitan area has roughly 25 million  people, with an economy estimated at about $1.4 trillion per year. If this  metropolitan area were a country, it would rank about 14th in the world in GDP  terms. 
A wise political doctrine known as  subsidiarity holds that public-policy challenges should be assigned to  the lowest level of government able to address them, thereby ensuring maximum  democratic participation in problem solving and the greatest opportunity to  tailor solutions to genuine local needs. While some issues – for example, a  national highway or rail system – require national-level problem solving, many  key challenges of sustainable development are best confronted at the urban  level. 
The world’s governments are now negotiating the Sustainable  Development Goals, which will guide the world’s development agenda from 2015  to 2030. In an important meeting on September 25, the United Nations General  Assembly agreed that the SDGs would be adopted at a global summit in September  2015, with the next two years used to select the priorities. 
An urban SDG, promoting inclusive,  productive, and resilient cities, would greatly empower tens of thousands of  cities worldwide to take up the cause of sustainable development for their own  citizens, their countries, and the world.